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Cold Starting O-470 - Funny Mag Behaviour

sj

sj

Staff member
Northwest Arkansas
Ok,

You may remember my summer thread about hot starting the O470 in the C-180. Well, I learned to hold my mouth right and it starts most of the time hot. Now I have a BIG cold starting problem with a wierd rough right mag for a few minutes after start. I'm thinking mag problem, but it just came through annual and one did not show up then.

Here is the deal: I have iridium (fine wire plugs) and I lean pretty agressively. I seriously doubt I have any buildup on the plugs, but when I cold start and finally get it going (it acts like it is not getting fuel, but fuel is running out of the carb onto the ground), the right mag is rough for about 4 minutes, then smooths out. Works great in flight, next start, same deal - even when the engine was only off for an hour. Almost sounds like timing of one mag is messed up, but then it runs smooth as glass in flight and after it warms up.

Even after a through pre-heat this plane is a bugger to start. Where would you look first? Carb problems? Mag problems?

I carry around a cessna jumper cable, battery charger, and a honda generator because I am afraid of getting stuck! I have used all three on different occasions!

Help me obi juan!

sj
 
Steve,

This probably doesn't have anything to do with your current problem, but you do have a piece of insulated pipe wrap tie-wrapped around your forward crossover induction tube, right????

If you don't....DO.

180's in cold are famous for running rough due to uneven fuel distribution.

That's not what this sounds like, but get some pipe wrap anyway.

MTV
 
Steve, This works good for me whe starting my "K" and also my old "A" which is like what you have. I have a 6 cyl. primer and give it 2 shots, then pull the prop through about 3 blades. Get in the plane and give it one more shot, then just barely crack the throttle and it usually starts in a blade or two. I have Bendix mags with impulses on both.
Marty
 
Thanks guys,

I have slicks, have tried the pull through method and it did not help, in fact, it seemed to get worse.

Also, I have a "J" not an "A".

Mike, when I say cold I am talking 40 degrees, not Fairbanks cold...

sj
 
Sounds like wet plugs. But wouldnt' explain a warm start an hour later. Wonder if your primer is somehow leaking and flooding your engine. Try no prime starts. Start it like its been flooded. Wide open mixture off then idle start normal. When was the last time the points gap was adjusted.
 
Not wet plugs, too many varying situations and conditions for it to be that - and as I said, Iridium plugs which in the other planes I have had them in have proven to be near bulletproof on all the other typcial plug problems.

Mags are what I suspect, but wondered if something jumped out at folks.

sj
 
Sounds more like you have somthing that is shorting out when cold. Is it possible that the plate attaching the leads to the mag has some dirt or something on it, and when it warms up the expantion changes the electrical path?

Have you tried changing plugs, all plugs go bad, some just burn up first.
 
Steve's Mags

Steve,

I had my mags rebuilt, and a new wiring harness installed soon after I bought my 180. The mags were running but shot - oddly they had not been overhauled at the recent engine major. It was cheap insurance to get the ignition system new again.

My 180 starts easy hot or cold, just a couple or three blades. When the old battery quit turning it over, and I needed a new battery, it was not an inconvenience to prop it (as you would a Super Cub) until the new battery came.

You might consider rebuilding the mags - the O-470 should give quick, satisfying starts.....

Bob Breeden


www.AlaskaAirpark.com
 
Bob,

You are probably right. I did put all new plugs in at annual (fine wire) and that really did not change much. Mags seem like the next logical step. I'll suffer through one more trip with it down to Gaston's next weekend then get 'er done.

Thanks folks!

sj
 
Are the primer nozzle's plugged up. I remove them every few years and soak them in Hoppy's gun cleaning solvent. Have found many completely plugged. Also how much time on the Slicks. I have started inspecting them evry 500 hrs and setting the E gap. Has fixed several cold weather starting problems. My Dad's was the worst. He ran the battery down several times and then was out hand proppping. :x
 
I agree with Bob.

I tried to get you to come get our 180 but NOOO!!!!! :wink: It starts just fine. Now its sitting in Colorado.

I hope you get it figured out.

Lance
 
Steve,

On the temperature thing, you were recently in South Dakota, no?

An airline friend from North Carolina was complaining of a rough running engine in cold winter temps between there and other points on the east coast. Pipe wrap on the forward crossover tube took care of that. It doesn't have to be Fairbanks cold to have this issue.

Also, in very cold temps, you may have to run some carb heat to keep it happy, but that is cold.

MTV
 
steve said:
(it acts like it is not getting fuel, but fuel is running out of the carb onto the ground)

sj
Click to expand...

I'd be figuring out why there's fuel running out of the carb.

Stewart
 
When fueling my 180 this afternoon, I was thinking about MTV's suggestion to insulate the balance tube( I have a big diameter one and a small one and can't see any difference when switching between the two) and was wondering how much warmer the intake air is after going through the venturi effect of the carb and into the intake runners vs. whats going around the uninsulated balance tube?
Marty
 
Marty,

I can tell you that if you don't insulate that balance tube, the thing will run like crap in cold temps. And it doesn't have to be arctic weather, either.

MTV
 
steve said:
Thanks guys,

I have slicks, have tried the pull through method and it did not help, in fact, it seemed to get worse.

Also, I have a "J" not an "A".

Mike, when I say cold I am talking 40 degrees, not Fairbanks cold...

sj
Click to expand...

You didn't tell us how old the slick mags were. 662's or newer style, but I'd guess mags too. Do you hear loud clicks (2) when you pull the prop thru. Seen quite a few impulses on the 470/520's get gummy and start sticking too. With gas dripping out, full throttle and mixture out and the engine will start in short order anyway with good mags. With bad mags you have to have the perfect mixture for a longer period of time for it to even fire.
 
S2D, you pretty much nailed it on the head. If the moon and the stars are not aligned with the sun, it won't go. I'm going to swap out the mags. Stay tuned....

sj
 
Steve,

WAAAAAAYYYYYY more time on this than you should :cry:

I will bring you a good starting Aircoupe and take away that difficult bird of yours :drinking:
 
poor starting 180

Steve,
You mentioned fuel running out of the carb on cold starts. Is that from over priming or are you pumping the throttle to prime? No way should you have to have raw fuel dripping to get it to start. Thats bad news. I agree with Mike V. that some C180 do run poorly when the front intake tube isn't wrapped/insulated-- The intake design on that continental is bad, the fuel/air distribution is very poor. Not to say that is your problem, if you had it pre-heated real well it probably isn't the problem. I would look into mag or carb issues. Let us know what the answer is?
Pete
 
Thanks fellers, the reason fuel is running out of the carb is because the plane was acting like it was not getting fuel, so I made sure that was not the case :oops:

New mags should be here tomorrow. Was ready to convert back to bendix, but could not find the parts. These mags have about 600 hours on them since 1991 - I am told that in the 91' vintage slicks the coils were not worth a hoot. I've talked to a couple folks about mags who think the slicks are throw away junk (of course, they are both rebuilders), but there are some PMA coils that you can put in the slicks that juice them up a bit on overhaul.

Also asked about "slick start". The answer in both cases was that is was covering up for a problem with the mags. If the mags are working right, you don't need a slick start.

Finally, recommended spark plug gap has been growing over the years (or so I am told). The problem is this decreases the life of plugs, and a mag with a weak coil just can't jump the distance. Going to have a look at the gaps too again while we are at it.

sj
 
Well, I wanted to give everybody an update on how this problem has been resolved. A brand spanking new set of slicks and yeee haw bo didley does she start nice - AND I am getting 40 or 50 more RPM on takeoff and climb (full forward on all levers), which surprised me. Also, the engine is running a LOT smoother. These were pretty high time older mags that I had on there. I have not tested it under all starting conditions yet, but so far things are looking good!

Thanks for all the help, folks!

sj

P.S. I am going to ask the guy who rebuilds my old mags for an autopsy of them.
 
Steve... I bet the old mags would have started better if you had heated them with a heat gun first. Defective electronic parts can sure change their personalities when their temps change. I have located many such traits with a heat gun. Just don't melt the whole world when you do it. :D
 
Cold starts...

We are using the 0-470 "R" engine. When the engine is cold, I have discovered that two pumps of the throttle, and ours starts almost on the first blade. The last time my forewarned son used the primer, he had a short lived- but scary- engine fire. He does it my way now. Pumping the throttle works for us with this engine, however, there are so many variables with the various engines, its really hard to make a correct generalization.

Mike
 
Mike, what is "cold" for you? :D

Cold for me (less than 50F.) on any O-470 is a full 4 shots of prime to get her started and keep her started.

It's known that throttle pumps only squirt into the lower manifold "Y".

I'm surprised our "mileage" is varying so greatly on the method to start a 470.

Just curious, that's why I asked. DAVE
 
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